Heavy Storm CHRISTIAN on 28 October 2013 Contact: Dr
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Heavy storm CHRISTIAN on 28 October 2013 Contact: Dr. Susanne Haeseler, Christiana Lefebvre; updated: 13 November 2013 Introduction In the last week of October 2013, the heavy storm CHRISTIAN moved across northern Europe (Fig. 1) causing destruction and travel chaos. Europe-wide it claimed at least 15 lives. Due to high wind speeds with hurricane force gusts, trees were toppled and buildings damaged. Power outages were reported not only from the United Kingdom and France, but also from northern Germany. Train services shut down temporarily, as e.g. in the southern United Kingdom and northern Germany, where the rail traffic was partly interrupted for several days. At London and Hamburg even the urban and underground railways were affected. Some streets were impassable. The Öresund Bridge between Denmark and Sweden was closed. Flights were cancelled. The ferry services between Dover and Calais as well as to some North Sea Islands shut down. Many Hallig inhabitants experienced “landunter” (i.e. flooding of the lowlands of the island). One feature of the storm was its southerly track across the United Kingdom. Another one was the high amount of damaged and toppled trees, because many deciduous trees were still in leaf due to mild weather conditions and therefore more vulnerable to strong winds. Fig. 1: Track of storm CHRISTIAN from 27 to 29 October 2013. [Source: DWD] 1 Consecutively used time specifications: MEZ = Central European Time (CET) UTC = Universal Time Coordinated (= MEZ minus one hour) Development of CHRISTIAN and wind gusts Storm CHRISTIAN formed on Saturday, 26 October, over the western Atlantic as a second- ary depression of the low-pressure system BURKHARD. On its way eastward, the remnants of ex-tropical storm LORENZO provided for an additional input of energy, benefiting the de- velopment of CHRISTIAN to an intense low-pressure system. With a forward speed of 1200 km in 12 hours, CHRISTIAN was a rapid moving low. On Sunday the 27th at 18 UTC, CHRISTIAN was located southwest of Ireland with a central pressure of 990 hPa. At 22 UTC, the strong cyclone made landfall in the southwest coast of Great Britain. With a further intensification (central pressure of 986 hPa), the first hurricane gusts were measured on the Breton coast with wind speeds up to 133 km/h (station Oues- sant-Stief). On the night to Monday, CHRISTIAN relocated north-eastwards and crossed the south of Great Britain. On Monday morning at 07 UTC, the centre of the storm with a pres- sure of 977 hPa was located over the East Midlands, near the city of Grimsby. At the same time, a ship on the English Channel reported the so far strongest gust of 168 km/h. On its further track across the southern North Sea heading towards Denmark, the first hurricane gusts on the German North Sea coast were measured at 11 UTC. The weather station Borkum-Süderstraße recorded a gust of 148 km/h. On the Brocken, the highest hill of the Harz mountain range, hurricane gusts were observed already before that time. Figures 2a and 2b show the surface analyses on 28 October 2013 at 00 and 12 UTC, Fig- ure 3 the satellite image at 14 UTC and Figure 4 the sustained wind at 14 UTC. Fig. 2a: Surface analysis North Atlantic/Europe on 28 October 2013, 00 UTC. [Source: DWD] 2 Fig. 2b: Surface analysis North Atlantic/Europe on 28 October 2013, 12 UTC. [Source: DWD] Fig. 3: Satellite image acquired on 28 October 2013, 14:02 UTC. [Source: DWD] 3 Fig. 4: Sustained (10-minute) wind across north-western Europe on 28 October 2013, 14 UTC. [Source: DWD] In Germany, heavy storm CHRISTIAN caused the highest wind speeds between 13 and 14 UTC (14 and 15 MEZ) over the German Bight and on the west coast of Schleswig- Holstein (Fig. 5). At that time, the centre of the storm was located off the northwest coast of Denmark. As there is no measurement at exactly this site, the actual central pressure can differ from the measurement of 968 hPa on the coast by a few hPa. At the same time, the weather station of Sankt Peter Ording recorded with a gust of 172 km/h the maximum value in the meteorological network of Deutscher Wetterdienst (German Weather Service). During the storm‘s further shift towards southern Scandinavia, the Danish weather station of Kegnaes Fyr, a lighthouse on the Baltic Sea coast near the border of Schleswig- Holstein/Germany, recorded a gust of 193 km/h. Northern Schleswig-Holstein was particularly hit by CHRISTIAN, because the highest gusts mostly reached hurricane force (at least 118 km/h). In southern Schleswig-Holstein and in Niedersachsen as well as in Mecklenburg-Vorpommern, gusts reached up to hurricane force in island and coastal areas. Hurricane-force gusts were also recorded at Hamburg, where the wind was strongest between 13 and 15 UTC (14 and 16 MEZ). In Mecklenburg-Vorpommern the wind speed was highest in the late afternoon. Storm gusts and accompanied damage occurred not only in northern Germany but also in the central parts. Peak wind speeds of more than 80 km/h were widespread registered in lowlands north a line Straßburg-Heilbronn- Hof-Dresden. 4 Fig. 5: Peak wind gusts between 13 and 14 UTC (14 and 15 MEZ) in northern Germany. [Source: DWD] The satellite image at 18 UTC shows the cloud swirl of CHRISTIAN across southern Scandi- navia (Fig. 6), where the centre was located at that time, and Figure 7 shows the wind rotat- ing anticlockwise around the centre of the storm. Fig. 6: Satellite image acquired on 28 October 2013, 18 UTC. [Source: DWD] 5 Fig. 7: Sustained (10-minute) wind across north-western Europe on 28 October 2013, 18 UTC. [Source: DWD] As would be expected in rapid moving lows like CHRISTIAN, the highest wind speeds were measured right (here south) of the centre, where displacement velocity and gradient wind (wind blowing around the centre of the low) add. On its track in north-eastward direction the cyclone weakened in the evening hours and the strong wind field did so as well. However, some central and northern European countries in the range of CHRISTIAN experienced a stormy night. Figures 8a-c show the fast relocation of the strong wind field of CHRISTIAN in north-eastern direction. 6 Fig. 8a: Maximum wind gusts (in km/h) on 28 October 2013, 12 UTC. [Source: DWD] Fig. 8b: Maximum wind gusts (in km/h) on 28 October 2013, 18 UTC. [Source: DWD] 7 Fig. 8c: Maximum wind gusts (in km/h) on 29 October 2013, 06 UTC. [Source: DWD] CHRISTIAN caused considerable rainfall amounts mainly in Schleswig-Holstein with region- ally more than 10 mm on the 28th (Fig. 9). Groß Wittensee, located southeast of Schleswig, even reported nearly 32 mm. Fig. 9: Precipitation total for Germany on 28 October 2013. [Source: DWD] 8 Wind speeds at Hamburg on 28 October Figure 10 shows the development of the wind speed (10-minute mean and peak gusts) at the airport Hamburg-Fuhlsbüttel. The highest recorded gust of the day was 120.2 km/h occurring between 14:00 and 14:10 UTC (15:00 and 15:10 MEZ). Figure 11 depicts the development of the wind speed (1-minute mean and maximum gust) and the air pressure reduced to NN at the Seewetteramt (Maritime Weather Office) in Hamburg-St. Pauli. It shows impressively the strong increase in wind speed after the passing of the cold front at about 13 UTC (14 MEZ). The highest gust of 66.4 kn (122 km/h) was recorded at 14:35 UTC (15:35 MEZ). Fig. 10: Development of the wind speed (in km/h) at Hamburg-Fuhlsbüttel on 28 October 2013. The sustained (10-minute) wind is coloured blue and highest gusts red. [Source: DWD] Fig. 11: Development of wind speed (in knots) and air pressure at Hamburg-St. Pauli on 28 October 2013. The sustained (1-minute) wind is coloured red brown, the highest gusts green and the air pressure light blue. [Source: DWD] 9 Storm surge in Schleswig-Holstein and Hamburg A storm surge alert was issued on account of CHRISTIAN. The water level at Hamburg- St. Pauli rose 1.74 m above the mean high water (Fig. 12) being not as high as suspected. © 2008 Bundesamt für Seeschifffahrt und Hydrographie Fig. 12: Current water level and forecast from 28 to 30 October 2013. [Source: BSH] There was also no severe storm surge in Schleswig-Holstein, and the damage to dykes was small. In a report of the Ministerium für Energiewende, Landwirtschaft, Umwelt und ländliche Räume Schleswig-Holstein it says [text translated]: “In the evening hours of 28 October 2013, a storm surge occurred on the west coast and the Elbe. At the levels of Husum and Eiderstedt, the maximum water level exceeded the mean high tide by more than two metres. At other discharge sites in the Elbe, the maximum water levels were about 1.7 metres above the mean high tide. On the islands and Halligen in the North Friesian Wadden Sea as well as in the region of Dithmarschen, the maximum water levels were just below 1.5 metres above the mean high tide. ... On the west coast of Sylt losses of the foredunes occurred and in some areas on Amrum low sand losses.“ Peak gusts and 10-minute sustained winds in Germany on 28 October 2013 Table 1 specifies peak gusts of Bft 11 (103 to 117 km/h) and Bft 12 (118 km/h or higher) rec- orded at German weather stations on 28 October, ordered by size, as well as the maximum sustained (10-minute) winds at these stations.